Transcript Forest Site Preparation

Forest Site Preparation
• Definition: Purposeful treatment of the site to prepare for the
regeneration process
– Applicable to natural and artificial regeneration
• Site preparation practices include:
– Remove unwanted vegetation, slash and stumps from a site
before/immediately following a regeneration method
– Any treatment modifies exiting vegetative or physical site conditions to
improve germination, survival, and subsequent growth of desired
seedlings
Silvicultural Objectives of Forest Site Preparation
•
Control competing vegetation
–
Most common
• Create a seedbed environment that favors target species
•
–
–
–
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Soil Scarification
Loosening of the upper soil or breaking up the organic layer
Removing undecomposed litter and humus to expose mineral soil
Mixing surface organic materials with mineral layers beneath them
Mechanically removing competing vegetation or interfering debris
Silvicultural Objectives of Forest Site Preparation
• Alter physical attributes of the rooting zone
– Reduce soil compaction
– Improve drainage
• Lower water table (ditches)
• Raise seedling rooting zone (bedding)
• Facilitate planting of seedlings
– Remove physical obstructions such as slash, standing trees, stumps
(this is especially important for machine planting)
• Aesthetics
How site preparation fits into a silvicultural system
Site Preparation Objectives in the Central
Hardwood Region
• Site preparation prior to final harvest
• Control competing vegetation
• Alter seedbed to promote establishment of advance tree reproduction
• Proactive removal of noncommercial trees that would inhibit seedling
development following a harvest
• Post-harvest site preparation
• Control competing vegetation
• Remove trees remaining from previous stand that are inhibiting
seedling development
• Alter seedbed to promote germination of light seeded species
• Prepare area for tree planting
Categories of Forest Site Preparation
1. Mechanical
a.
b.
c.
d.
e.
Competition control
Slash manipulation + competition control
Seedbed manipulation
Competition control + seedbed manipulation
Alter physical attributes of the rooting zone
2. Chemical
a.
Competition control
3. Prescribed Fire
a.
Competition control + seedbed and slash manipulation
Mechanical Site Preparation
Mechanical Competition Control
Manual Felling:
Mechanical Competition Control
Manual Girdling:
Mechanical Competition Control
Shearing: Cuts down standing vegetation using a large tractor
with KG blade or V-blade
Mechanical Competition Control
Shearing: Cuts down standing vegetation using a large tractor
with KG blade or V-blade
• Benefits
– Can facilitate planting, but usually inadequate alone
– Provides some competition control, but is usually inadequate without
follow-up treatment
• Due to resprouting hardwood species
• For planting, shearing is usually to facilitate further
mechanical site prep, such as rake-and-pile or drum chopping
• Shearing is also used to complete silvicultural clearcutting in
hardwoods
Mechanical Slash Manipulation and Competition Control
Drum chopping: use a large cylindrical drum with sharp blade,
pulled by a large tractor
• Breaks debris into smaller pieces, gets it closer to the ground
(for more effective burning);
• Destroys some rootstocks (usually preceded by shearing)
Drum chopping
• Benefits:
– Provides some competition control, but it may be poor or inconsistent,
due to problems with sprouting
• chopping is typically followed by burning, which increases
effectiveness
– Provides some facilitation of planting, which may be greatly improved
by burning
– Provides some improvement in soil conditions (increased infiltration of
surface runoff, reducing erosion)
Mechanical Slash Manipulation and Competition Control
Rake-and-pile (root-raking, windrowing: use a large tractor
with a root-rake to move surface debris and stumps, and to rip
out rootstocks
• It normally follows shearing
• Most commonly, debris is piled into windrows
– May burn these for more efficient space utilization
• Benefits
– Facilitates planting
– Fair to good competition control
Rake-and-pile (root-raking, windrowing)
• Potential problems:
– Erosion/sedimentation
– Movement of topsoil (often results in a reduction in site productivity)
• Countermeasures:
–
–
–
–
–
Avoid rake-and-pile on steep slopes and highly erodible soils
Put windrows on contour
Do not remove litter layer unnecessarily
Use only skilled and careful machine operators
Do not use a straight blade for raking!
Mechanical Slash Manipulation and Competition Control
Mastication: mechanical grinding of logging slash, whole trees,
and brush
• Used commonly in fuels reduction treatments
Mechanical Seedbed Manipulation and Competition Control
Disking: done with large heavy disks, pulled by a large tractor
• Knocks down small material, rips up smaller rootstocks
• Benefits:
– May provide good competition control
– Provides some facilitation of planting
– Can decrease compaction
• disking has a high potential for erosion when used in hilly terrain
• it should be on contour
• Provides a good seedbed for direct seeding or natural seeding (farm
tractor)
Mechanical Alteration of Rooting Zone
• Bedding: combination of plowing and disking to create raised
beds for planting seedlings
• Usually follows rake-and-pile
• Benefits
– Improves soil aeration, both by raising above a high water table and by
breaking soil compaction
– Facilitates planting
– Gives additional competition control
– On uplands, positive benefits of bedding include:
• can reduce erosion losses and sedimentation (if beds are on
contour),
• concentrate organic matter near seedlings
• reduce compaction of heavy soils.
• Allow beds to settle for six weeks before planting
Mechanical Alteration of Rooting Zone
• Subsoiling (ripping): utilizes a long (24-48 "), narrow, sharp
plow for cutting through compact soil or a restrictive soil pan
• Usually follows other methods, or is used in old fields that
have a plowpan
• Benefits
– Improves root development
– Facilitates planting
– Must be on contour to avoid erosion
Combination Treatments
• Combination treatments
The Savannah “3-in-1 plow”- employs a specialized combination
of ripping, plowing, and bedding, (often with shearing) in one
pass
Soil Scarification to Improve Oak Establishment
• What is Soil Scarification?
The use of mechanized equipment to create a shallow soil
disturbance in desired areas that incorporates acorns into the
soil, while providing competition control.
Factors Influencing Oak Seedling Establishment
• Acorn Production
– Highly variable with large seed crops 2 to 10 years
• Predation: mammals, birds, insects
• Seed moisture content
– Temperature and moisture of forest floor
– Acorn position in forest floor
• Leaf litter depth
Acorn Positions in Forest Floor
•
Unfavorable:
1. on litter layer surface
2. positioned within a thick litter layer
•
Favorable:
1. buried 1 to 2 inches deep in soil
2. in contact with mineral soil, covered with leaf litter that is
not too thick
–
Protect against desiccation, extreme temperatures, and
predation
Why Use Soil Scarification for Oak Regeneration?
• Increase germination through incorporation
– Provides protection from predators
– Improves germination conditions
• Provides competition control
– Enhance seedling growth
– Influence species composition
Disk Scarification
So. IL Bottomland Oak Disking – Results
Impact of Treatment on Oak Seedling Density
Control
Scarified
Seedlings Ha-1
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
Stand A
Stand B
Pretreatment
Stand A Stand B
Year 1
So. IL Bottomland Oak Disking - Poison Ivy
So. IL Bulldozer and Brush Rake Study
Mature, mixed oak upland forest
• Scarification treatment:
– 78 hp crawler tractor
– 8 ft, 6-tooth brush rake
– Rake inserted into the soil
approx. 4 inches
– Operation damaged or uproot
midstory trees
Bulldozer/Brush Rake Scarification
So. IL Bulldozer/Brush Rake Study – Results
Impact of Treatment on Oak Seedling Density
6000
Seedlings Ha-1
5000
Control
Scarified
4000
3000
2000
1000
0
Pretreatment
Year 1
So. IL Bulldozer/Brush Rake Study – Results
Impact of Treatment on Midstory
Overall Trends
• The results suggest scarification may:
– Increase germination and initial establishment
– Influence competing vegetation
– Enhance competitive position of oak seedlings
– Be a useful management tool in both upland and bottomland
forests
Note: abundant acorns must be present
Chemical Site Preparation
Reasons for Using Chemical Site Preparation
• Kill dense or unwanted vegetation that:
– Interfere with survival and development of desired species
– Impede silvicutlural operations
• Kill or desiccate ground vegetation to improve fuel conditions
for prescribed burning
• Prevent understory development
– Competition and/or fuel reduction reasons
• Inhibit seed germination of weed species
Advantages of Chemical Site Preparation
• Effectively kills a broad array of weeds and competing plants
• Can kill targeted species when applied with proper timing,
dosage, and formulation
• Prevents sprouting from stumps and root systems
• Does not disturb surface or affect the inherent site productivity
potential
• Works equally well in treating large or small areas in a number
of ways and times of the year
• Proven cost-effective, particularly for broadcast and other
mechanized applications over large areas
Site Preparation
and Stand Yield
Chemical Site Preparation
Herbicide Labels
• Labels are required legal documents: uses other than those
listed are illegal
• All forestry herbicides must pass a rigorous approval process
for EPA (sets standards for effectiveness and safety
• Important information that is listed on herbicide labels:
– Ingredients
– Precautionary statement
• uses a signal word (Caution, Warning, or Danger)
• only Velpar L and Garlon 3A have "Danger", due to potential eye damage
– May include a restricted use designation
– Information and directions for approved uses (including species "controlled")
– Instructions for storage and disposal
Herbicide Toxicity
• Toxicity: Those labeled for forestry uses are low in toxicity,
are non-persistent, and do not bioaccumulate
• They are targeting plants, usually blocking or overstimulating
plant enzymes
• None are toxic to birds or mammals at expected levels of
exposure or ingestion
• LD50: dose (wt/body wt) fatal to 50% of test organisms.
Lower # more toxic
• They are rapidly tied up or broken down in biological and soil
systems
Herbicide Application
• Methods
– Broadcast
• Aerial
• Ground based machines
• Backpack sprayer
– Spot or strip
– Individual stem
• Cut surface application
• Bark application
• Chemicals used should be labeled for the application
Herbicide Tank Mixes
• Tank mixes: two or more herbicides are mixed together
– Wider spectrum of control
– Most commonly applied as broadcast foliar and/or soil-active
• Aerial most efficient (helicopter), but requires large tracts, or
coordination of several smaller tracts
• tractors or skidders (with sprayers or spreaders), backpack sprayers,
or hand carried spreaders are also used
– Do not plant tree seedlings for 3-6 months after most soil-active
chemicals (esp. for Tordon, Velpar)
– Commonly followed by hot prescribed fire (“brown and burn”) {in
order to facilitate planting}
– Tank mixes common with broader spectrum of control and quick
brownup
• Arsenal/Accord, Tordon/Garlon
Herbicide Tank Mixes
Application in spots or strips ("bands")
• Hand carried sprayers or spreaders, spot guns, tractor-mounted
sprayers or spreaders
Prescribed Fire for Site Preparation
Prescribed Fire for Site Preparation
Primary Uses
• Reduce slash, debris, and undecomposed litter, and release
nutrients in accumulated organic materials
• Kill interfering vegetation or reduce understory plants to alter
visual qualities in a stand
• Influence plant succession or increase ecological diversity by
perpetuating fire-dependant plant communities
• Reduce accumulation of hazardous fuels
• Reduce the thickness of forest floor or expose mineral soil
Uses of Burning for Site Preparation
Secondary Uses
• Open cone and other fruiting structures to release seeds
– Species with seratonous cones (e.g., jack pine and lodgepole pine)
• Destroy pests and harmful organisms and the habitats that
sustain them
• Increase water yields by altering the kind and size of
vegetation and reducing transpiration
• Induce sprouting of surviving vegetation to improve cover,
browse or forage production
Effects of Prescribed Burning
Effects will depend on:
• Amount and nature of fuel
– Pine litter more flammable than hardwood litter
• Size of vegetation to be killed {poor top kill if >3" diameter}
• Number of sproutable rootstocks (maximum kill for one burn usually
around 20%, less for a winter burn)
• Timing of burn
– most kill in growing season (optimum just after leaf out), least in dormant
season;
– best consumption with least green or living vegetation, i.e., in fall/winter or
after herbicide browning
– higher erosion potential with fall/early winter burn (soil stays bare all winter)
– late spring burn will impact ground nesting birds (e.g., wild turkeys)
Potential problems in using prescribed burning
• Scheduling: need proper fuel conditions, weather, and
available manpower
• Requires experienced supervision for planning and
implementation
• Smoke management potential problems: air pollution, P.R.,
legal restrictions and liability
• Containment issues and liability
• Fire may damage or kill residual trees